Different 2D ultrasound calculation methods to evaluate tongue volume for prediction of difficult laryngoscopy

Abstract

Background and Aims: The aim of the study was to evaluate and compare three different ultrasonographic calculation methods for tongue volume in a real time 2D ultrasonography and correlate with Modified Cormack-Lehane grading observed under direct laryngoscopy. Methods: This prospective observational study was conducted in a tertiary care institute. Tongue volume was assessed ultrasonically in 50 adult patients using three techniques in all the patients undergoing surgery under general anesthesia and correlated with Modified Cormack-Lehane grading. In METHOD A, the tongue volume was calculated as multiplication of mid sagittal cross-sectional area and width in transverse plane; METHOD B, Cross-sectional area obtained in vertical plane was multiplied with the maximum width of tongue in transverse plane; METHOD C. the volume was calculated by multiplying length, width, and height in vertical, transverse, and mid-sagittal/oblique plane, respectively. The analysis was done using Statistical Package for Social Sciences (SPSS) version 21.0. Receiver operating characteristic (ROC) curve was used to find out cutoff point of different methods for predicting difficult laryngoscopy. Results: The specificity and sensitivity of three different methods were statistically compared and area under the receiver operating characteristic (ROC) curve for method A, B, and C was 0.562, 0.502, and 0.548, respectively. Conclusion: In our study, we found all three methods to calculate tongue volume to be equally good to assess difficult laryngoscopy.